Electronic device manufacturers attempt to fit or squeeze as many integrated circuit devices as possible into the limited real estate of larger devices manufactured therewith, for instance, mobile devices such as mobile phones, which themselves are getting progressively thinner and more compact over time due to market preferences and demands. Presently, mobile device manufacturers compete based on producing ever more powerful yet smaller, slimmer and more compact devices. Consequently, more often than not, multiple integrated circuit devices, chips, or die are embedded or stacked into a single semiconductor component package, thereby forming what can be defined as a packaged composite device. There is a greater likelihood that one or more portions of a packaged composite device can become warped, distorted, or too thick during the course of its manufacture. This affects the ability of the manufacturer to accurately ascertain whether the packaged composite device will meet dimensional and reliability requirements prior to mounting the packaged composite device into or onto portions of a slim mobile device. Furthermore, the extent of and profile of the warpage or distortion of the packaged composite devices inspected may indicate problems in the manufacturing process, such as errors in device embedding or stacking. If a package is exceedingly thick, it may indicate that the multiple devices stacked in the package may not have been correctly stacked, or may indicate poor adhesion or mounting during the manufacturing process.
In the past, in association with the optical inspection of packaged composite devices, manufacturers relied on Total Package Thickness (TPT) as a parameter or measure of the thickness or height of the packaged composite device, the measurement of which includes the height of the underlying ball grid array or pads for the package. This parameter alone has become insufficient to accurately determine if a package will fit and/or likely reliably operate in a mobile device, as the possible manners in which a packaged composite device can dimensionally vary as a result of manufacturing process inconsistencies and/or errors can result in the false rejection of acceptable or good devices, as well as the acceptance or passage of defective or likely unreliable devices when relying on TPT as the sole measure for characterizing packaged composite device height.
With respect to optical inspection, warpage of the package together with how the package is seated or held in position during an inspection process may result in a larger package height reading, which may cause the package to be rejected even though the package may actually be mountable in or on a mobile device, as the slightly elastic nature of the package mold compound allows for some compression and flattening of the package and the devices contained therein without affecting the electrical or structural integrity of the entire package.
Conventional optical inspection of packaged devices such as packaged composite devices requires the packaged device to be suction or vacuum-held by a nozzle against a planar reference surface during inspection. This results in compression of the package against the reference surface. The resultant distortion of the package as a result of compression against the plane of the reference surface can either increase the package warpage (thereby artificially increasing the actual TPT) or reduce the package warpage (thereby artificially reducing the actual TPT) during inspection, resulting in erroneous TPT measurements or readings. It must be noted that if a 3D scan is performed on the top and/or bottom surfaces of a package when held against a reference plane or held down at the inspection area by vacuum or suction force against a reference seating plane, the captured 3D profile of the top and/or bottom surfaces of the package will not provide the correct or required surface topology of the package.
It is necessary to find a way for manufacturers to determine if a packaged composite device meets the dimensional requirements for it to be mounted and reliably used in a slim mobile device without the problems, limitations, and inconsistencies mentioned above.